BACKGROUND: Efficacy of a multi-strain direct-fed microbial product (PoultryStar® ME; PS) and a xylanase enzyme product on the dietary energy utilization efficiency and resulting performance in broiler chickens was evaluated. Apart from performance parameters, cecal and serum metabolites and activities of hepatic enzymes involved in energy metabolism were also determined. Ross 308 chicks were fed one of four experimental diets [control (CON), CON + PS, CON + xylanase and CON + PS + xylanase] using a 2×2 factorial arrangement from 1–21 days of age.

RESULTS: Cecal proportions of propionate and butyrate, as well as total short-chain fatty acid concentration were increased (P<0.01) by PS suggesting increased fermentation of dietary fiber. Both additives reduced (P<0.01) serum non-esterified free fatty acids, while PS reduced (P<0.01) serum triglyceride. Hepatic glycogen concentration was increased (P<0.01) by both additives. Changes in these serum metabolites and hepatic glycogen indicate the influence of additives in swiftly transitioning the birds from fasting to feeding metabolism. The activity of hepatic glucose-6-phosphate dehydrogenase (G6PDH) was increased (P<0.01) by PS. Elevated hepatic glycogen andG6PDH activity indicate increased glucose-sparing potential. Feed conversion ratio (FCR) was lowered by both additives, while themagnitude of reduction was higher with the combination.

CONCLUSION: The combination worked synergistically, compared to their individual effects, to increase dietary energy uptake and hepatic energy retention. The combination additively increased the FCR, suggesting involvement of synergistic modes of actions.